Process for the production of a ribbon filament yarn of regenerated cellulose



July 16, 1963 P. LEWIS 3,09

PROCESS FOR. PRODUCTIONOF A RIBBON FILAME'NT YAR F REGENERATED CELLULOSE ed Sept. 7, 1961 Inventor Peter LQ S MAM Attorneys United States Patent 3 097 914 PROCESS FOR THE PROnUcTIoN OF A RIBBON EILAMENT YARN 0F REGENERATED CELLU- OSE Peter Lewis, Healing, Grimsby, England, assignor to Courtaulds Limited, London, England, a British com- Filed Sept. 7, 1961, Ser. NO. 136,580 Claims priority, application Great Britain Sept. 7, 1960 4 Claims. (Cl. 18-54) This invention relates .to the production of regenerated cellulose filaments having an elongated, cross-seotion and referred to hereafter as ribbon filaments.

It is frequently possible to change the shape of the cross section of filaments spun from viscose, by altering the shape of the holes of the jet through which the viscose is extruded. However, it does not always follow that the shape of the filaments is similar to the shape of the holes. For example, when the jet holes are slots, ribbon filaments are obtained only when each slot is at least seven times as long as it is broad, otherwise the filaments tendto a circular cross-section.

The difiiculty and expense of making multi-slot jets for ribbon filament spinning, increases to such an extent as the width of a slot decreases, that a slot width of 0.001 of an inch is the that could reasonably be employed in routine commercial production. A jet having slots of 0.01 of an inch by 0.001 of an inch has been used to make ribbon filaments h-avin'g deniers of from 8 to 10, but lower deniers were not easily attained. For all practical purposes, therefore, the minimum denier of ribbon filaments produced from slotted jets is about 8.

The present process makes possible the production of lower filament denier ribbon filament yarns without using expensive multi-slot jets.

Accordingly the present invention is a process for the production of a ribbon filament yarn of regenerated cellulose comprising extruding viscose having a cellulose to caustic soda ratio of at least 1, and at a salt point between 4 and 6 through a multihole jet the holes of which have no re-en-trant segment in their cross-sections into a coagulating bath maintained at a temperature of 40 C. to 60 C. and containing at least 24 percent of sodium sulphate, from 9 to 12 percent of sulphuric acid and not more than 0.02 percent of zinc sulphate as an impurity, drawing the incompletely regenerated filaments from the bath and subsequently completely regenerating the filaments.

Jets having circular holes are particularly preferred for [their ease of manufacture and relative cheapness.

It appears that the elongated cross-sections of ribbon filaments made by the presented process, arises from the chemical action of the bath and is not a result of the filaments being drawn over guides or godets in the early stages of the process. Certainly the acid concentration and the high concentration of sodium sulphate in the bath are critical, for the ribbon characteristic of the filaments rapidly disappears as the acid concentration falls below 9 percent or rises above 12 percent or as the sodium sulphate falls from 24 percent to, say, 20 percent.

The ratio of the cellulose to the caustic soda in the viscose is also important. The higher that ratio is, the smoother the elongated section of the filament, whereas viscoses in which the ratio is less than 1 cannot be spun into ribbon filaments by the present process.

The salt figure of the viscose becomes more critical as the ratio of cellulose to caustic soda in the viscose is reduced. For example ribbon filaments can be made from viscose containing 8.3 percent cellulose and 5.8 percent caustic soda, i.e. a viscose having a cellulose to caustic soda ratio of more than 1.4, when the salt figure is between about 4 and 6, but the salt point of a viscose containing 7.6 percent cellulose and 6.2 percent caustic soda, has to be between about 4 and 4.5. Thus, those viscoses according to this invention which have a cellulose to caustic soda ratio between 1 and about 1.25 should also have a salt point of from 4 to 4.5.

The invention is illustrated by the following examples:

Example 1 A viscose containing 7 .6 percent of cellulose and 6.2 percent of caustic soda was aged to a salt figure of 4 and then extruded through a 5 0 hole jet into a bath maintained at 55 C., and containing 12 percent of sulphuric acid, 27 percent of sodium sulphate and no zinc sulphate. The jet holes were circular, each having a diameter of 0.005 of an inch. The filaments were drawn through the bath for 24 inches before being taken from the bath and lapped three times on a take-up godet having a peripheral speed of 54 metres per minute. The filaments were stretched by 30 percent in passing to a second godet having a peripheral speed of 70 metres per minute. After leaving the second godet the filaments were collected in a centrifugal box in the form of a cake which was washed successfully with dilute acid and Water.

The dried filaments had the following average properties:

Conditioned (65 percent relative humidity at 25 0.)

Wet

Tenacity -g.p.d Extensibility percent Example 2 The procedure of Example 1 was followed, using a viscose containing 8.3 percent of cellulose and 5.8 percent of caustic soda, aged to a salt figure of 5.5. The bath contained 10.5 percent of sulphuric acid, 24 percent of sodium sulphate and no zinc sulphate and was maintained at a temperature of 55 C.

The averaged properties of the filaments produced were:

Conditioned (65 percent relative humidity at 25 0.)

Wet

Tenacity g.p.d. Extensibility percent The filaments had elongated cross-sections six times as wide as they were thick, and a denier of 5.9.

When the bath acid concentration was 9 percent or 12 percent the effect was still noticeable, but the 10.5 percent concentration bath produced a smoother more uniform elongation.

Viscoses of salt FIGURES 4, 5 and 6 were also used successfully, but viscoses of salt figures 3 and 7.5 could not be used.

What I claim is:

1. A process for the production of a ribbon filament yarn of regenerated cellulose, consisting of extruding viscose having a cellulose to caustic soda ratio of at least 1 and at a salt point between 4 and 6, through a multihole jet the holes of which have no re-entrant segment in their cross-sections into a coagulating bath maintained at a temperature of 40 C. to 60 C. and containing at least 24 percent of sodium sulphate, from 9 to 12 percent of sulphuric acid and not more than 0.02 percent of zinc sulphate as an impurity, drawing the incompletely regenerated filaments from the bath and subsequently completely regenerating the filaments.

2. A process as claimed in claim 1 in which the filaments are extruded through circular holes in the jet.

3. A process as claimed inclaim 1 in which the viscose has a cellulose to caustic soda ratio of between 1 and 1.25 and a salt point of between 4 and 4.5.

4. A process as claimed in claim 1 in which the cellulose to caustic soda ratio is at least 1.4.

References Cited in the file of this patent UNITED STATES PATENTS 1,366,166 Criggal Jan. 18, 1921 1,964,659 Brumbcrger June 26, 1934 2,327,516 Fink Aug. 24, 1943 2,535,044 Cox Dec. 26, 1950 FOREIGN PATENTS 481,565 Great Britain Mar. 11, 1938 

1. A PROCESS FOR THE PRODUCTION OF A RIBBON FILAMENT YARN OF REGENERATED CELLULOSE, CONSISTING OF EXTRUDING VISCOSE HAVING A CELLULOSE TO ACUSTIC SODA RATIO OF AT LEAST 1 AND AT A SALT POINT BETWEEN 4 AND 6, THROUGH A MULTIHOLE JET THE HOLES OF WHICH HAVE NO RE-ENTRANT SEGMENT IN THEIR CROSS-SECTIONS INTO A COAGULATING BATH MAINTAINED AT A TEMPERATURE OF 40* C. TO 60* C. AND CONTAINING AT LEAST 24 PERCENT OF SODIUM SULPHATE, FROM 9 TO 12 PERCENT OF SULPHURIC ACID AND NOT MORE THAN 0.02 PERCENT OF ZINC SULPHATE AS AN INPURITY, DRAWING THE INCOMPLETELY REGENERATED FILAMENTS FROM THE BATH AND SUBSEQUENTLY COMPLETELY REGENERATING THE FILAMENTS. 